Development and Internal Validation of a Prediction Model for Difficult Laryngoscopy Using Ultrasound‐Derived Factor in Comatose Patients

Abstract

ObjectivesThe distance from skin to the hyoid bone (DSHB) and skin to the anterior commissure of vocal cords (DSAC) are reliable parameters for pre‐operative airway ultrasound assessment in awake patients and can be assessed in comatose patients. This study aimed to inspect its feasibility and accuracy in predicting difficult laryngoscopy for comatose patients.MethodsA prospective cohort study included patients with a Glasgow Coma Scale (GCS) of ≤8 who underwent emergency tracheal intubation between November 2019 and August 2020. The outcome was difficult laryngoscopy and classified according to the Cormack–Lehane grading.ResultsA total of 151 patients were included in the study. Fifty‐two (34.4%) patients were categorized as having difficult laryngoscopy. The DSHB add DSAC (hereinafter referred to as the “DSBAC”) was superior to either parameter alone in the predictive performance, and the optimal cut‐off value was 1.90. To optimize the predictive value, DSBAC (adjusted odds ratio [OR]: 7.76; 95% confidence interval [CI]: 2.88–20.94; P < .001), GCS (adjusted OR: 1.39; 95% CI: 3.93–26.28; P = .039), mandibular retraction (adjusted OR: 8.20; 95% CI: 1.92–35.09; P = .005) and edentulous (adjusted OR: 4.23; 95% CI: 1.40–12.80; P = .011) were included in a multivariable model and constructed a nomogram. Discrimination and calibration statistics were satisfactory, with C‐index above 0.80 from both model development and internal validation.ConclusionsUltrasound‐derived factor, DSBAC, can be easily assessed and help predict difficult laryngoscopy among comatose patients. A simple nomogram including only four clinical items exhibited excellent discrimination performance and was useful when comatose patients underwent emergency tracheal intubation.